1. Field of the Invention
This invention relates to a wiper apparatus used for wiping a windshield of, for example, a motor vehicle with a wiper blade and, more particularly to a wiper apparatus provided with an improved switching mechanism for spraying washing fluid in the moving direction of the wiper blade swinging reciprocatively, at all times.
2. Description of the Prior Art
Heretofore, there has been used a wiper apparatus as shown in FIG. 5 and FIG. 6, which is disclosed in Japanese Utility Model Disclosure (KOKAI) No.2-117956/90.
In a wiper apparatus 20 shown in FIGS. 5 and 6, a pivot shaft 30 supported rotatably through a pivot holder 30a fixed to a vehicle body 50 is connected to a motor shaft 32a of a wiper motor 32 through a link 31 at the base end thereof, and connected with a base end of a wiper arm 34 fitted with a wiper blade 33 at the opposite end thereof.
The wiper arm 34 is provided with a first side washer nozzle 40 on the right side adjacent the opposite end thereof as viewed in FIG. 5, which is on the leading side when the wiper blade 33 moves toward the upper turning position B from the lower turning position A, and is provided with a second side washer nozzle 41 on the left side thereof as viewed in FIG. 5, which is the leading side when the wiper blade 33 moves toward the lower turning position A from the upper turning position B. The respective washer nozzles 40 and 41 are connected to a switching mechanism 36 shown in FIG. 6 through respective feed pipes 45 and 46 and the switching mechanism 36 is connected to a washer pump 43a of a reservoir 43 through a feed pipe 44.
The switching mechanism 36 is comprised mainly of a valve casing 36a formed interiorly with a fluid chamber 36a1 and a valve element 36a6, and is provided with a reservoir duct 36a2 communicating with the fluid chamber 36a1 on the upper face of the valve casing 36a and nozzle ducts 36a3, 36a4 communicating with the fluid chamber 36a1 on the upper side of the valve casing 36a in FIG. 5. The switching mechanism 36 is housed in the wiper arm 34 at the position spaced from the pivot shaft 30 as shown in FIG. 5.
The switching mechanism 36 is provided with the valve element 36a6 having a switching lever 36a5 protruding outwardly from the valve casing 36a at the center part of the fluid chamber 36a1, and so designed that the nozzle duct 36a3 or 36a4 may be blocked alternatively according to the movement of the valve element 36a6 around a valve shaft 36a7 by shifting the switching projection 36a5.
The nozzle ducts 36a3 and 36a4 are connected to ends of the feed pipes 45 and 46 respectively, and the opposite ends of the feed pipes 45 and 46 are connected to the first and second side washer nozzles 40 and 41, respectively. The feed pipe 44 is connected to the reservoir duct 36a2 on the upper side of the wiper arm 34 shown also in FIG. 6.
Furthermore, the pivot holder 30a is provided with switching projection 30a1 and 30a2 to contact with the switching lever 36a5 of the switching mechanism 36 at the time that the wiper blade 33 arrives at the lower turning position A and the upper turning position B, respectively, for switching over the valve element 36a6 alternatively when the wiper arm 34 swings reciprocatively together with the switching mechanism 36.
In the wiper apparatus 20 having the aforementioned structure, by actuating the wiper motor 32 according to the ON-operation of a wiper switch (not shown), the rotational movement of the motor shaft 32a is converted into the angularly oscillating movement of the pivot shaft 30 through the link 31, thereby swinging the wiper arm 34 reciprocatively. The windshield 35 is wiped between the lower turning position A and the upper turning position B with the wiper blade 33 pressed against the windshield 35 by elasticity of a spring disposed to the wiper arm 34.
In this state, by actuating the washer pump 43a of the reservoir 43 according to the ON-operation of a washer switch (not shown), the washing fluid stored in the reservoir 43 is fed to the fluid chamber 36a1 of the switching mechanism 36 through the feed pipe 44. When the valve element 36a6 in the fluid chamber 36a1 is rotated in the clockwise direction round the valve shaft 36a7 in FIG. 5 according to the contact of the switching lever 36a5 with the switching projection 30a1 when the wiper blade 33 arrives at the lower turning position A, and the nozzle duct 36a4 on the left side in FIG. 5 is blocked by the valve element 36a6 while the wiper blade 33 is moving toward the upper turning position B from the lower turning position A. Therefore, the washing fluid supplied to the fluid chamber 36a1 of the switching mechanism 36 from the reservoir 43 is fed into the first side washer nozzle 40 through the nozzle duct 36a3 and the feed pipe 45, and sprayed toward the windshield 35 in the leading direction of the wiper blade 33 through the first side washer nozzle 40.
Next, when the wiper blade 33 moves toward the upper turning position B from the lower turning position A and arrives at the upper turning position B, the switching lever 36a5 of the valve element 36a6 comes in contact with another switching projection 30a2 and the valve element 36a6 is rotated in the anticlockwise direction about the valve shaft 36a7 in FIG. 5, whereby the valve element 36a6 blocks the nozzle duct (going side duct) 36a3 so as to stop the spraying of the washing fluid through the first side washer nozzle 40 and opens the nozzle duct 36a4. Accordingly, the washing fluid supplied to the fluid chamber 36a1 of the switching mechanism 36 is fed into the second side washer nozzle 41 through the nozzle duct 36a4 and another feed pipe 46, and sprayed toward the windshield 35 in the leading direction of the wiper blade 33 moving to the lower turning position A from the upper turning position B through the second side washer nozzle 41.
Furthermore, when the wiper blade 33 moves toward the lower turning position A from the upper turning position B and arrives at the lower turning position A, the switching lever 36a5 comes in contact with the switching projection 30a1 and the valve element 36a6 blocks the nozzle duct 36a4 to stop the spraying of the washing fluid through the returning side washer nozzle 41 and opens the nozzle duct 36a3. In such a manner, the washing fluid is always sprayed in the leading direction of movement of the wiper blade 33 by switching the washer nozzle alternatively between the first side washer nozzle 40 and the second side washer nozzle 41.
However, in the aforementioned wiper apparatus 20, the reservoir duct 36a2 to be connected with the feed pipe 44 protrudes upwardly from the wiper arm 34, and the feed pipe 44 is so structured as to be exposed on the outside of the vehicle body 50 and is moved swingingly together with the reciprocative movement of the wiper arm 34. Therefore, there are problems in that an external view of the wiper apparatus 20 is spoiled by the feed pipe 44 and the feed pipe 44 can be easily damaged and/or disengaged from the reservoir duct 36a2 of the switching mechanism 36. The switching projections 30a1 and 30a2 for contacting the switching lever 36a5 are provided on the pivot holder 30a, but there is another problem since a wide space is required between the switching projections 30a1 and 30a2 in order to contact with the switching lever 36a5 of the switching mechanism 36 disposed away from the pivot shaft 30. Furthermore, there is a problem in that it requires much labor to repair or exchange the switching mechanism 36 since the switching mechanism 36 is disposed in the wiper arm 34 and it is necessary to detach the wiper arm 34 connected with the feed pipe 44. In addition to the above, there is a further problem in that timing adjustment for switching the spraying direction of the washing fluid is spoiled when foreign matter such as dust or the like collects between the switching projection 30a1 and 30a2.